Optimizing raster operation functions during print job processing

ABSTRACT

Methods for processing print jobs in rendering devices include modifying a raster operation function to have fewer variables than originally specified by the print job. Processing may also include executing the modified function and determining how many variables the function originally includes and whether such is one or more. Preferably, the modifying of the function includes determining whether a variable of the function has a black or white identity, such as a black or white ink or a black or white image, stencil or character. It may also include determining whether a destination variable remains unaltered in a to-be-painted area. Printers having stored computer executable instructions for performing the steps are also disclosed as are host devices that may direct or control the printer to perform the same.

CROSS REFERENCE TO RELATED APPLICATION

Pursuant to 37 C.F.R. §1.78, this application is a divisional and claims the benefit of the earlier filing date of application Ser. No. 10/811,209 filed Mar. 26, 2004, now U.S. Pat. No. 7,817,302 entitled “Optimizing Raster Operation Functions During Print Job Processing.”

FIELD OF THE INVENTION

The present invention relates to achieving optimization during processing of print jobs in a rendering device, such as a printer. In one aspect, it relates to optimizing raster operation functions by modifying their form originally specified by the print job. In another aspect, it relates to modification according to various identities of the function variables.

BACKGROUND OF THE INVENTION

The art of printing with rendering devices, such as laser or other printers, is relatively well known. In general, printing results by processing a print job, typically in the well known form of a printer description language (PDL), to create bitmaps that are sent to printing mechanisms to obtain hard copy outputs. Among other things, the PDL specifies a raster operation function describing how to apply pixel coloring for to-be-printed objects of the print job. Often, this function embodies a math or logic function as a Boolean expression, for example, when the PDL is of PCL language type or an algebraic expression for PDF languages. As is known, a PCL language has 256 possible logic functions while a PDF language has 16 math functions. In any raster operation function, however, sometimes the function includes a multiplicity of variables including, but not limited to, a destination variable, a to-be-printed object variable and/or an ink or coloring variable. Yet, the more variables a function has, the more processing and more memory required therefor. Accordingly, a need exists in the printing arts for achieving optimization of raster operation functions, especially for minimizing processing and memory requirements.

SUMMARY OF THE INVENTION

The above-mentioned and other problems become solved by applying the principles and teachings associated with the hereinafter described methods and apparatus for achieving optimization of raster operation functions during processing of print jobs in rendering devices, such as printers. Methods of optimizing include modifying raster operation functions to have fewer variables than originally specified by the PDL print job. Preferably, the modification occurs as a result of determining whether a variable of the function has a black or white identity, such as a black or white ink or a black or white image, stencil or character, or whether a destination variable remains unaltered in a to-be-painted area. Additionally, determining how many variables a function has and whether such is one or more may be performed before the function modification occurs. Printers having stored computer executable instructions for performing the method of the invention are also disclosed as are host devices that may direct or control the printer to perform the same.

These and other embodiments, aspects, advantages, and features of the present invention will be set forth in the description which follows, and in part will become apparent to those of ordinary skill in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart in accordance with the teachings of the present invention for optimizing a raster operation function if possible;

FIG. 2 is an expanded flow chart in accordance with the teachings of the present invention for optimizing a raster operation function if possible;

FIG. 3 is a flow chart in accordance with the teachings of the present invention for optimizing a raster operation function if a variable has a certain identity or a variable has only one destination variable;

FIG. 4 is a flow chart in accordance with the teachings of the present invention for optimizing a raster operation function if a destination variable has a certain identity;

FIG. 5 is a diagrammatic view in accordance with the teachings of the present invention of a representative operating environment in which the invention may be practiced;

FIG. 6 is a diagrammatic view in accordance with the teachings of the present invention of a rendering device in the form of a laser printer.

FIG. 7 is a flow chart in accordance with the teachings of the present invention indicating when the graphics engine preferably renders to-be-printed objects for a given to-be-printed page of a print job into device specific pages in memory;

FIG. 8 is a diagrammatic view in accordance with the teachings of the present invention of a display list object;

FIG. 9A is a diagrammatic view in accordance with the teachings of the present invention of a display list having pluralities of objects;

FIG. 9B is a diagrammatic view in accordance with the teachings of the present invention of an alternate embodiment of a display list having pluralities of objects; and

FIG. 10 is a diagrammatic view in accordance with the teachings of the present invention of a display list having pluralities of objects and a root.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process, electrical, mechanical and/or software changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims and their equivalents. In accordance with the present invention, methods and apparatus for achieving optimization of raster operation functions during the processing of print jobs are hereinafter described.

In general, a raster operation function becomes optimized in accordance with the invention if the function can have its variable dependency reduced. In one embodiment, FIG. 1, optimizing a raster operation function begins by assessing whether the function is one or more variable dependent, step 10. If not, the function remains as presented or specified by the PDL, for example, step 12. If so, if the function can then become modified into fewer variable dependencies, step 14, it is so modified at step 16. In FIG. 2, this process can be preceded with a determination of the actual number of variables of the raster operation function, step 20, and can be followed at step 22 with the processing of the print job through execution of the raster operation function so modified at step 16.

In either instance, raster operation function optimization, by reducing variable dependency, includes the following representative examples whereby an original function specified with a given number of variables becomes modified into fewer variable dependencies and such is recited as the outcome of the expression. Although the following examples typify a multiple-variable raster operation function modified into a single or zero variable function, the invention is not so limited and embraces all embodiments whereby functions are modified into fewer variable dependency. As a preliminary matter, however, the raster operation functions in the examples are presented as a function F(D, S, P) on a pixel-by-pixel basis of a to-be-printed page, where D is the to-be-printed page or destination variable; S is a to-be-printed object or object variable of the print job, such as a stencil; and P is the ink, coloring or filling variable of the print job relative to the object variable, such as a solid color for filling the boundaries of the stencil S or an image for filling the stencil boundaries.

In further specificity, the object variable corresponds to whether the to-be-printed object of the print job is an image, such as a jpeg, a stencil, such as a rectangle, or a character (a, b, c . . . x, y, z, 0, 1, 2, . . . ). In other embodiments, it could correspond to a group of related objects. It may also include information useful in processing the object such as a region bounding box. The destination variable corresponds to the physical location and geography of the to-be-printed page on which the to-be-printed object will reside. The ink variable corresponds generally to how to “paint” each pixel within the boundaries or region of the object variable. In turn, the painting of each pixel means to blend three colors of the destination variable, the object variable and the ink variable based on a logic function F(D, S, P).

EXAMPLE 1

In a PCL raster operation function ROP 252, the function is the Boolean expression: P or S in a RGB color space. In the event P is a black ink only (0, 0, 0 in RGB), S is the exclusive outcome of the expression and the destination page is exclusively overwritten with S. In the event P is a white ink only (1.0, 1.0, 1.0 in RGB), P is the exclusive outcome of the expression and the destination page is exclusively overwritten with P. In the event P is neither a black nor a white ink, and if S is an all black image, a character or a stencil, then the outcome of the expression is exclusively P.

EXAMPLE 2

In a PCL raster operation function ROP 90, the function is the Boolean expression: P xor D in a RGB color space. If P is a black ink, the outcome of the expression is D. If D is white or unaltered in the to-be-painted area of the to-be-printed page, the outcome of the expression is the invert of P.

EXAMPLE 3

In a PCL raster operation function ROP 136, the function is the Boolean expression: D and S in a RGB color space. If S is an all white image, the outcome of the expression is D. If S is an all black image, the outcome of the expression is to use a black ink on the destination page. If D is white, or unaltered in the to-be-painted area of the to-be-printed page, the outcome of the expression is S.

EXAMPLE 4

In a PCL raster operation function ROP 160, the function is the Boolean expression: D and P in a RGB color space. If P is a black ink, the outcome of the expression is P. If P is a white ink, the outcome of the expression is D. If D is white, or unaltered in the to-be-painted area of the to-be-printed page, the outcome of the expression is P.

EXAMPLE 5

In a PCL raster operation function ROP 184, the function is the Boolean expression: P xor (S and (D xor P)) in a RGB color space. If S is an all white image (1.0, 1.0, 1.0 in RGB), the outcome of the expression is D. If S is an all black image (0, 0, 0 in RGB), a character or a stencil, the outcome of the expression is P. If P is black (0, 0, 0 in RGB) then the outcome of the expression is simplified to S AND D. If P is black (0, 0, 0 in RGB) and S is white (1.0, 1.0, 1.0 in RGB) the outcome of the expression is exclusively D.

EXAMPLE 6

In a PCL raster operation function ROP 226, the function is the Boolean expression: D xor (S and (P xor D)) in a RGB color space. If S is an all black image, a character or a stencil, the outcome of the expression is D. If S is an all white image, the S outcome of the expression is P.

EXAMPLE 7

In a PCL raster operation function ROP 170, the function is the Boolean expression: D in a RGB color space. The outcome of the expression is no processing (NOP) required.

EXAMPLE 8

In a PCL raster operation function ROP 0 or ROP 255, the function is to paint zero (black) on the destination page or paint one (white), respectively. Thus, the function need not become modified and can remain as originally specified by the print job in accordance with step 12 (FIG. 1).

EXAMPLE 9

In a PCL raster operation function of “logical or,” “logical and” or “logical exclusive or” the incoming ink value or variable P onto the destination page, if the incoming ink variable is black (0, 0, 0 in RGB) for the “logical or” and “logical exclusive or” function, the outcome of the function is no processing (NOP) required. If the incoming ink variable is white (1.0, 1.0, 1.0 in R, G, B) for the “logical and,” the outcome of the function is NOP. If the incoming ink variable is white (1.0, 1.0, 1.0 in R, G, B) for the “logical or,” the outcome of the function is white. If the incoming ink variable is white (1.0, 1.0, 1.0 in R, G, B) for the “logical exclusive or,” the outcome of the function is the inverse of the other variable.

Appreciating that, in many of the foregoing examples, black and white identities of the variables of the raster operation function allow the function to become modified into a fewer number of variables, the flow chart of FIG. 3 exemplarily shows modification of a function by examining black or white identities of the variables. Preferably, a black or white identity refers to black or white ink variable or a black or white object variable such as a black or white image, stencil or character. At step 30, if a variable of the function has a black or white identity, the function becomes modified into fewer variables, step 32. If no variable has a black or white identity, the function becomes examined for other identities lending themselves to the possible modification or optimization of the function, step 34. In FIG. 4, one such other identity to be examined is whether the destination variable remains unaltered in a to-be-painted area of the to-be-printed page, step 40. If so, the function becomes modified to have fewer variables, step 42. If not, the function becomes examined for still other identities lending themselves to the possible modification or optimization of the function, step 44. Of course, the determination, of whether the function variables have a black or white identity or a destination variable only (step 30) or whether the function has a destination variable unaltered in a to-be-painted area (step 40), can occur in any order or substantially simultaneously. Skilled artisans can also envision other identities of the variables of the raster operation function that will allow the modification of the function into a fewer variable dependency.

Appreciating users of the invention will likely accomplish some aspect of the methods in a computing system environment, FIG. 5 and the following discussion are intended to provide a brief, general description of a suitable computing environment in which either the structure or processing of embodiments may be implemented. Since the following may be computer implemented, particular embodiments may range from computer executable instructions as part of computer readable media to hardware used in any or all of the following depicted structures. Implementation may additionally be combinations of hardware and computer executable instructions. Further, implementation may occur in an environment not having the following computing system environment so the invention is only limited by the appended claims and their equivalents.

When described in the context of computer readable media having computer executable instructions stored thereon, it is denoted that the instructions include program modules, routines, programs, objects, components, data structures, patterns, trigger mechanisms, signal initiators, etc. that perform particular tasks or implement particular abstract data types upon or within various structures of the computing environment. Executable instructions exemplarily comprise instructions and data which cause a general purpose computer, special purpose computer, or special or general purpose processing device to perform a certain function or group of functions.

The computer readable media can be any available media which can be accessed by a general purpose or special purpose computer or device. By way of example, and not limitation, such computer readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or any other medium which can be used to store the desired executable instructions or data fields and which can then be accessed. Combinations of the above should also be included within the scope of the computer readable media. For brevity, computer readable media having computer executable instructions may sometimes be referred to as software or computer software.

With reference to FIG. 5, an exemplary system for implementing the invention includes a general purpose computing device in the form of a conventional computer 120. The computer 120 includes a processing unit 121, a system memory 122, and a system bus 123 that couples various system components including the system memory to the processing unit 121. The system bus 123 may be any of the several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory includes read only memory (ROM) 124 and a random access memory (RAM) 125. A basic input/output system (BIOS) 126, containing the basic routines that help to transfer information between elements within the computer 120, such as during start-up, may be stored in ROM 124. The computer 120 may also include a magnetic hard disk drive 127, a magnetic disk drive 128 for reading from and writing to removable magnetic disk 129, and an optical disk 131 such as a CD-ROM or other optical media. The hard disk drive 127, magnetic disk drive 128, and optical disk drive 130 are connected to the system bus 123 by a hard disk drive interface 132, a magnetic disk drive interface 133, and an optical drive interface 134, respectively. The drives and their associated computer-readable media provide nonvolatile storage of computer readable instructions, data structures, program modules and other data for the computer 120.

Although the exemplary environment described herein employs a hard disk, a removable magnetic disk 129 and a removable optical disk 131, it should be appreciated by those skilled in the art that other types of computer readable media exist which can store data accessible by a computer, including magnetic cassettes, flash memory cards, digital video disks, removable disks, Bemoulli cartridges, random access memories (RAMs), read only memories (ROM), and the like. Other storage devices are also contemplated as available to the exemplary computing system. Such storage devices may comprise any number or type of storage media including, but not limited to, high-end, high-throughput magnetic disks, one or more normal disks, optical disks, jukeboxes of optical disks, tape silos, and/or collections of tapes or other storage devices that are stored off-line. In general however, the various storage devices may be partitioned into two basic categories. The first category is local storage which contains information that is locally available to the computer system. The second category is remote storage which includes any type of storage device that contains information that is not locally available to a computer system. While the line between the two categories of devices may not be well defined, in general, local storage has a relatively quick access time and is used to store frequently accessed data, while remote storage has a much longer access time and is used to store data that is accessed less frequently. The capacity of remote storage is also typically an order of magnitude larger than the capacity of local storage.

A number of program modules may be stored on the hard disk 127, magnetic disk 129, optical disk 131, ROM 124 or RAM 125, including but not limited to an operating system 135, one or more application programs 136, other program modules 137, and program data 138. Such application programs may include, but are not limited to, word processing programs, drawing programs, games, viewer modules, graphical user interfaces, image processing modules, intelligent systems modules or other known or hereinafter invented programs. A user enters commands and information into the computer 120 through input devices such as keyboard 140 and pointing device 142. Other input devices (not shown) may include a microphone, joy stick, game pad, satellite dish, scanner, camera, personal data assistant, or the like. These and other input devices are often connected to the processing unit 121 through a serial port interface 146 that couples directly to the system bus 123. It may also connect by other interfaces, such as parallel port, game port, firewire or a universal serial bus (USB).

A monitor 147 or other type of display device connects to the system bus 123 via an interface, such as a video adapter 148. In addition to the monitor, computers often include other peripheral output devices, such as speakers (not shown). Other output or rendering devices include printers, such as a laser printer 161, for producing hard copy outputs of sheets 1, 2, 3 . . . N of paper or other media, such as transparencies. In general, the hard copy output appears as a representation of what a user might view in a print preview screen 163 of an original program application displayed on the monitor. In this instance, the hard copy appears as three side-by-side objects, especially a red (interior-filled) vertically oriented rectangle, a green ring with a white interior and a blue (interior-filled) triangle, and all reside in a non-overlapping fashion near a bottom 7 of sheet 1. In one embodiment, the printer 161 connects to the computer or host device by direct connection to the system bus via a cable 167 attached to parallel port interface 165. In other embodiments, it connects via the serial port interface, USB, Ethernet or other. Often times a driver, for installing necessary software on the computer 120 for the computer and printer to interface properly and to provide a suitable user interface with the printer via the monitor, becomes inserted as the optical disk 131, the magnetic disk 129 or can be downloaded via the internet or retrieved from another entity as a file. Some forms of the present invention contemplate the driver as storing computer executable instructions for executing the methods of the present invention.

During use, the computer 120 may operate in a networked environment using logical connections to one or more other computing configurations, such as a remote computer 149. Remote computer 149 may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer 120, although only a memory storage device 150 having application programs 136 has been illustrated. The logical connections between the computer 120 and the remote computer 149 include a local area network (LAN) 151 and/or a wide area network (WAN) 152 that are presented here by way of example and not limitation. Such networking environments are commonplace in offices with enterprise-wide computer networks, intranets and the Internet, but may also be adapted for use in a mobile environment at multiple fixed or changing locations.

When used in a LAN networking environment, the computer 120 is connected to the local area network 151 through a network interface or adapter 153. When used in a WAN networking environment, the computer 120 typically includes a modem 154, T1 line, satellite or other means for establishing communications over the wide area network 152, such as the Internet. The modem 154, which may be internal or external, is connected to the system bus 123 via the serial port interface 146. In a networked environment, program modules depicted relative to the computer 120, or portions thereof, may be stored in the local or remote memory storage devices and may be linked to various processing devices for performing certain tasks. It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used. Moreover, those skilled in the art will appreciate that the invention may be practiced with other computer system configurations, including host devices in the form of hand-held devices, multi-processor systems, micro-processor-based or programmable consumer electronics, network PCs, minicomputers, computer clusters, main frame computers, and the like.

With reference to FIG. 6, the rendering device or printer 161 of FIG. 5 is described in more detail. In one embodiment, the printer includes the following functional blocks: an input interface 210; pluralities of PDL emulators 212-1, 212-2 . . . 212-N; a graphics engine 214; an engine interface 216; and print mechanisms 218, including one or more lasers. Of course, the printer has other well known functional components (not shown) to effectuate printing of sheets 1, 2, 3 . . . N, of a print job including a controller often embodied as an ASIC or microprocessor, system memory, buffers, memory card slots/readers, a user-input control panel with discrete buttons and/or software, and the like. Some of these other components may actually be the source of print job. The printer connects to the computer 120 (FIG. 5) via IR, wirelessly, or a cable connected to one of its many input/output (I/O) ports 220. Representative I/O ports include a parallel port, a serial port, a USB port, or a network port, such as Ethernet, LAN, WAN or the like. In addition to or in substitution for the computer 120, the printer can also interface with other host devices. For example, it may interface directly with a digital camera, a personal data assistant, an optical code reader, a scanner, a memory card, or other known or hereafter developed software or apparatus.

During use, as is known, when the host or other device has a print job ready for printing, the host sends data to the printer in a form ready for processing by the printer. Often, this data embodies the well known form of a PDL and includes the raster operation function previously described. Some of the more well known forms of PDLs include Hewlett Packard's printer control language (PCL), PCLXL, Adobe's POSTSCRIPT, Canon's LIPS, IBM's PAGES and IPDS, to name a few. Yet, the printer does not know how many host or other devices are connected to it, on which I/O port(s) they may reside and in what form the PDL print job will arrive. Accordingly, the input interface 210 of the printer performs the following two well known functions. First, it assesses (by looping through the I/O ports) which, if any, of the I/O ports have a print job for the printer and, if a print job exists, locks onto such port. Second, it supplies the print job to the appropriate PDL emulator 212 in accordance with the PDL language type. As shown in FIG. 6, PDL emulators within the printer preferably exist as one emulator per one PDL language type (e.g., one PDL emulator 212-1 for PCL, one PDL emulator 212-2 for POSTSCRIPT, etc.). Downstream, the PDL emulator communicates/interfaces with the graphics engine 214. Generally speaking, the PDL emulator interfaces between the computer and the graphics engine to interpret the language of the PDL file, of any given print job, for the benefit of the graphics engine.

To actually invoke the lasers of the printer or other print mechanisms 218 (including, but not limited to, paper pick mechanisms, rollers, belts, photoconductive members, fusers, sheet feeders, toner cartridges, duplexers, and the like), the graphics engine 214 communicates directly with an engine interface 216. Preferably, the graphics engine supplies a bitmap rendered in device specific color and halftoned. The engine interface, in turn, supplies the requisite information, usually in the form of signals, to the print mechanisms to produce hard copy sheets 1, 2, 3 . . . N, for example.

For any given print job, the PDL file (through the PDL emulator) will eventually signal or indicate to the graphics engine that the graphics engine has been presented with or received all to-be-printed objects for a given page of a print job. With reference to FIG. 7, this step 410 then invokes the graphics engine to render all the to-be-printed objects for that given page into a device specific page in memory, step 412. Preferably, this memory corresponds to the graphics engine dedicated memory M but may be any memory, local or remote, the graphics engine has access to. In an alternate embodiment, the rendering of the to-be-printed objects into device specific pages of memory occurs at the completion of receipt of more than one to-be-printed page of the print job or occurs before the completion of receipt of a single to-be-printed page.

In one preferred embodiment, the rendering of to-be-printed objects occurs first by having the graphics engine build, create or otherwise construct a display list having one or more to-be-printed objects for a given to-be-printed page. In essence, the display list comprises pluralities of data structures found in addresses or locations linked in memory that together describe a given to-be-printed object(s) and a to-be-printed page. A display list root begins the display list and points to the first object. The first object then points to the second object and so on until all objects are connected, in memory, for a given to-be-printed page of a print job. Preferably, all object(s) on the display list occur in the same exact order that the PDL file presented them to the graphics engine.

In more specificity, FIG. 8, a display list object 500 for any given object preferably includes, but is not limited to, the attributes of object type 502, object region 504 and object ink 506. Attributes, as used herein, are typically presented to the graphics engine in accordance with the language type of the PDL. Attributes, however, may also be indirectly influenced by the printer or operator, via the driver or operator panel 162 on the printer 161, for example. A next pointer 508 is also included on the display list object 500 but does not substantively represent an attribute of the object. It merely points to the next object on the display list as will be described later in more detail. The attributes themselves point to specific other memory locations or addresses 510, 512, 514 that more particularly define the object type, the object region and the object ink, respectively.

In one embodiment, the object type attribute corresponds to whether the to-be-printed object is an image, such as a jpeg, a stencil, such as a rectangle, or a character (a, b, c . . . x, y, z, 0, 1, 2, . . . ). In other embodiments, it could correspond to a group of related objects. The object region attribute corresponds to the physical location of the to-be-printed object on the to-be-printed page and the geography of the object type, such as the pixel dimensions of a rectangular stencil. It may also include information useful in processing the object such as a region bounding box. The object ink attribute corresponds generally to how to “paint” each pixel within the object region. With more specificity, the painting of each pixel means 1) what color to apply to each pixel for that to-be-printed object; and 2) how to apply pixel coloring in instances when pixels of multiple objects overlap one another on the to-be-printed page. In category 2), this typically includes the raster operation function previously described. Although shown in a given order on the display list object 500, the attributes may occur in any order desirable and the actual memory locations representing the attributes of the object need not be contiguous or sequential. With reference to FIG. 9A, a more comprehensive display list 600 is shown with pluralities of display list objects 500-1, 500-2, 500-3 linked together for a given to-be-printed page of a print job via the functionality of the next pointer 508-1, 508-2, 508-3 as previously discussed. In FIG. 9B, the objects (generically 500) of the display list 600 may alternatively be doubly linked via the functionality of both next and previous pointers 608-1, 608-2, 608-3, etc. In still other embodiments, the pointers need not point to immediately preceding or following objects and/or each object 500 may have pointers in addition to those shown. Of course, each object 500 still includes their other attributes and ellipses between the next and previous pointers indicate this feature.

With reference to FIG. 10, the display list 600 for a given to-be-printed page may also include a display list root 700 constructed by the graphics engine, and stored in memory, that precedes the first display list object 500-1 and points thereto. In general, 20 the root describes the physical to-be-printed page and the virtual page in memory corresponding thereto. In one embodiment, the root 700 includes attributes for describing this, including a to-be-printed page description attribute 702 and a flag attribute 704.

The page description 702 attribute includes information such as the size of the to-be-printed page (e.g., 8.5″×1141 , A4, etc.), page type (e.g., paper, transparency, glossy, etc.) and the like. It may also contain information specifying the color space in which to-be-printed objects will become blended. The flag 704 attribute becomes set or not (e.g., on or off) for the entirety of the to-be-printed page to indicate whether any of the raster operation functions within the ink attributes 506-1, 506-2, 506-3, etc., of any of the display list objects 500-1, 500-2, 500-3, etc., include a difficult, complex or otherwise “hard” processing operation. If they do, the flag is set. If they do not, the flag is not set. As used herein, a hard processing operation means any raster operation function, previously described, having two or more variables.

As such, the modification of the raster operation function to have a variable dependency less than originally specified by the print job will implicate the setting or not of the flag attribute in a printer having an architecture described above. As is described in more detail in the assignee's (Lexmark International, Inc.) application entitled “Processing Print Jobs,” filed on Mar. 26, 2004, having Ser. No. 10/810,004, now U.S. Pat. No. 7,835,080, and incorporated herein by reference, downstream print job processing occurs down one processing route if the flag is set and down another processing route if the flag is not set. Since processing occurs much more easily without the flag set, being able to modify the raster operation function to have fewer variables, especially less than two, lends tremendous advantage in this type of architecture. This does not mean, however, the invention is only limited to printer architectures of the type having flags set or not.

In an alternate embodiment, the flag 704 attribute can become set or not for the entirety, or a partiality, of the to-be-printed page to indicate any other criterion or criteria such as the presence or absence, the on or off, or meeting of a condition, or not, in any of the display list objects 500. Still alternatively, the flag attribute may become set or not depending upon whether the math or logic function is a Boolean or an algebraic equation in accordance with the popular PCL or PDF languages. In addition, the condition may reside in an attribute of an object other than or in addition to the ink attribute 506. The condition may also appear in the display list root in addition to or in the absence of a condition appearing in one or more of the display list objects.

Hereafter, the graphics engine renders the to-be-printed objects into device specific pages in memory. In one embodiment, this includes the graphics engine ascertaining the object type attribute 502-1 of the to-be-printed object; ascertaining the object region attribute 504-1; and converting the color information, on a pixel-by-pixel basis for that to-be-printed object, into the device specific colors (e.g., CMYK) as previously described. Next, it performs well-known halftone operations for the to-be-printed object so it will appear properly to the human eye when viewed as a hard copy output. Next, the memory addresses or locations corresponding to that object, i.e., the display list object 500-x, are released or freed so that the graphics engine or other structure can use them for future operations as necessary. If additional to-be-printed objects appear on the display list that require rendering, the graphics engine repeats the process until all to-be-printed objects are rendered in memory. At this point, the graphics engine can hand-off the bitmap, in device specific colors and halftoned, directly to the engine interface 216 (FIG. 6) to invoke the print mechanisms 218 of the printer 161 for producing a hard copy sheet. Of course, if additional to-be-printed pages, e.g., 2, 3 . . . N existed in a given print job, the graphics engine could wait until all to-be-printed pages became rendered before executing the hand-off.

In general, it is known to have either host based control of printing or to have device or printer based control of printing. Heretofore, printer based control has been exclusively described. In an alternate embodiment, however, the foregoing could be implemented through host-based control wherein the printer driver, installed on the host from some sort of software media, e.g., optical disk 131 (FIG. 5), alone or in combination with the computer 120, could perform the above-described processing through the implementation of computer-executable instructions on the driver or elsewhere. In still another embodiment, although the foregoing has been described in relationship to a laser printer, e.g., 161, no reason exists why this could not extend to inkjet printers, fax machines, copy machines, monitors, or other output-type rendering devices that provide output renditions for a given input.

The present invention has been particularly shown and described with respect to certain preferred embodiment(s). However, it will be readily apparent to those skilled in the art that a wide variety of alternate embodiments, adaptations or variations of the preferred embodiment(s), and/or equivalent embodiments may be made without departing from the intended scope of the present invention as set forth in the appended claims. Accordingly, the present invention is not limited except as by the appended claims. 

1. A method for processing a PCL print job in a rendering device, said PCL print job specifying a raster operation function, comprising determining whether said function has one or more variables, wherein said function has at least two of a destination variable, an object variable and an ink variable, further including modifying said function to have fewer said variables than specified by said PCL print job, said modifying including reducing said function to a single variable.
 2. The method of claim 1, further including executing said modified function.
 3. The method of claim 1, wherein said modifying further includes determining whether at least one of said variables of said function has a black or white identity.
 4. The method of claim 3, further including determining whether said ink variable is black or white.
 5. The method of claim 3, further including determining whether said object variable is black or white.
 6. The method of claim 5, further including determining whether said object variable is one of a character, a stencil and an image.
 7. The method of claim 1, wherein said modifying further includes determining whether said destination variable is unaltered in a to-be-painted area.
 8. A method for processing a PCL print job in a rendering device, said PCL print job specifying a raster operation function, comprising: determining whether said function has at least two of a destination variable, object variable and an ink variable; modifying said function to have fewer said variables than specified by said PCL print job such that said function has no more than a single variable; and executing said modified function.
 9. The method of claim 8, wherein said modifying further includes determining whether at least one of said object variable and said ink variable has a black or white identity.
 10. The method of claim 8, wherein said modifying further includes determining whether said destination variable is unaltered in a to-be-painted area.
 11. A printer including a processor and memory which stored computer executable instructions for executing the steps comprising: determining whether a raster operation function presented to said printer has at least two variables of a destination variable, an object variable and an ink variable; and modifying said function to have fewer said variables, said fewer variables resulting in said function having no more than one variable; and executing said modified function.
 12. The method of claim 11, further including setting a flag or not in response to said modifying.
 13. The method of claim 11, further including determining whether said function requires a hard processing operation or not.
 14. The method of claim 11, further including constructing a display list having a plurality of to-be-printed objects, each having an ink attribute where said modified function resides.
 15. The method of claim 8, wherein said modified function has a single variable. 